1. Field of the Invention
The present invention relates to the art of shutters for buildings or homes, such being mounted to openings in buildings.
2. Description of the Related Art
Generally, there are types of such shutters for buildings wherein the shutter curtain is arranged to descend by its own weight in the event that a brake is released, such as is with the case of weight shutters. With these type of shutters, the shutter curtain is opened and closed by means of driving operation by opening/closing gear. In such cases, the opening/closing gear is comprised of an electric motor, brake, and governor (speed-adjusting device). The arrangement is such that in the event that the brake is released in conjunction with detection of an abnormality such as fire, the speed of the shutter curtain is adjusted by a governor so that the shutter curtain is automatically closed while preventing the shutter curtain from falling by its own weight, thereby securing a fire prevention section.
However, such shutters for buildings are arranged such that a driving force transmitting mechanism such as a chain or the like transmits the diving force from the output shaft of the opening/closing gear to a winding drum, and in the event that this driving force mechanism is broken, the falling prevention function of the aforementioned governor does not work at all, and the shutter falls under its own weight.
In order to deal with this problem, arrangements have been proposed wherein means for preventing falling of the shutter curtain in the event that the drive chain is broken and so forth are provided, such as disclosed in Japanese Unexamined Patent Publication No. 61-146391 and Japanese Unexamined Patent Publication No. 62-180196.
However, such known arrangement require a dedicated falling prevention device, resulting in an increased number of parts and a complicated structure, and further, space must be separately provided for the falling prevention device, increasing the size of the overall shutter apparatus.
Moreover, the shutter curtain which has been caught by the falling prevention device functioning is suspended in an emergency half-opened state, with no further means to close the shutter. Further yet, since this state is an abnormal state, maintenance by a specialist is required, and until the specialist arrives on the site, a guardsman or the like must be posted to prevent people from entering or exiting through the half-opened shutter, and moreover yet, leaving the shutter in this half-opened state at nighttime poses further security problems. The present invention has been made in order to deal with the aforementioned problems in the known art.